Conventional Winchester type disc drives include a plurality of vertically aligned rotating information storage discs, each of which has at least one associated magnetic head that is adapted to transfer information between the 10 disc and an external computer system. Each head is carried by an elongated flexure arm. The flexure arms are vertically aligned and are each attached to a common head positioner assembly. The head positioner assembly is adapted to move the heads back and forth in unison across the face of the vertically aligned discs. The head positioner assembly may be either rotationally mounted, or may take the form of a carriage that is free to move back and forth along a single axis. In either case, the head positioner assembly is adapted to precisely position the heads relative to the magnetic discs.
Since the magnetic heads and flexure arms, as well as the information storage discs are vertically aligned, the positions of the heads relative to their associated information storage discs may be regulated by accurately tracking the position of a single one of the heads. The tracking head is generally referred to as the servo head and its associated flexure arm is known as the servo flexure. A disc controller is used to accurately position the heads using information that the servo head reads from its adjacent magnetic disc. It will be appreciated that one of the important characteristics of a disc drive is the average speed at which it can access information on the discs. Therefore, the controller that drives the head positioner assembly must have a rapid response. This is accomplished by utilizing feedback control from the servo head with a relatively large gain.
In disc drives that incorporate rotationally mounted head positioner assemblies, the heads and flexure arms undergo rapid angular acceleration and deceleration as they move back and forth across the discs. Conventional flexures have several drawbacks, one of which is that they are relatively flexible laterally and torsionally. When the head positioner assembly is moved very quickly, the resonant frequencies of the flexures are frequently stimulated causing the heads to oscillate back and forth. Such resonant oscillations limit the speed at which information can be retrieved since the computer must wait until the oscillations are damped before reading information from or writing information onto the disc. These resonance problems are particularly troublesome when they occur in the servo flexure since the feedback controller that regulates the position of the head positioner assembly will be provided with incorrect information as to the position of the heads and thus will tend to over or under compensate for the actual head position. Therefor, the resonance problems tend to reduce the effectiveness of a tight controller and slow down the overall disc access speed.